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Mast Cell Activation Syndrome (MCAS)

What is Mast Cell Activation Syndrome (MCAS)?

Mast Cell Activation Syndrome (MCAS) occurs when the mast cells in your body release too much of the substances inside them at inappropriate times.

Mast cells are part of your immune system. They’re found in your bone marrow and around the blood vessels in your body. When you’re exposed to stress or danger, your mast calls respond by releasing substances called mediators. Mediators cause inflammation, which helps your body heal from an injury or infection.

If you have MCS, your mast cells release mediators too frequently and too often. 

What are the symptoms of Mast Cell Activation Syndrome (MCAS)? 

Too many mediators can cause symptoms in almost every system in your body. However, the most commonly affected areas include your skin, nervous system, heart, and gastrointestinal tract. 

Depending on how many mediators are released, your symptoms can range from mild to life-threatening.

Symptoms include:

    • skin: itching, flushing, hives, sweating
    • eyes: itching, watering
    • nose: itching, running, sneezing
    • mouth and throat: itching, swelling in your tongue or lips, swelling in your throat that blocks air from getting to your lungs
    • lungs: trouble breathing, wheezing
    • heart and blood vessels: low blood pressure, rapid heart rate
    • stomach and intestines: cramping, diarrhea, nausea, abdominal pain
    • nervous system: headache, dizziness, confusion, extreme tiredness

In severe cases, you can develop a life-threatening condition called anaphylactic shock. This causes a rapid drop in your blood pressure, a weak pulse, and narrowing of the airways in your lungs. It usually makes it very hard to breath and requires emergency treatment.

What causes Mast Cell Activation Syndrome (MCAS)? 

Researchers aren’t sure what causes MCAS. However, a 2013 study noted that 74 percent of participants with MCAS had at least one first-degree relative who also had it. This suggests that there’s likely a genetic component to MCAS.

How is Mast Cell Activation Syndrome (MCAS) diagnosed?

MCAS can be hard to diagnose because its symptoms overlap with those of many conditions.  

To be diagnosed with MCAS, you must meet the following criteria: 

    • Your symptoms affect at least two body systems and are recurrent, and there’s no other condition causing them. 
    • Blood or urine tests performed during an episode show you have higher levels of markers for mediators than you do when you aren’t having an episode.
    • Medications that block the effects of the mast cell mediators or their release make your symptoms go away. 

Before diagnosing your condition, your doctor will review your medical history, give you a physical exam, and run blood and urine tests to rule out any other causes of your symptoms. 

What are the treatments for Mast Cell Activation Syndrome (MCAS)?

There is currently no cure for MCAS.

Where can I find out more about Mast Cell Activation Syndrome (MCAS)? 

MCAS Articles

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